title: Water stress-induced xylem hydraulic failure is a causal factor of tree mortality in beech and poplar.
abstract: OBJECTIVE
  Extreme water stress episodes induce tree mortality, but the physiological mechanisms causing tree death are still poorly understood. This study tests the hypothesis that a potted tree's ability to survive extreme monotonic water stress is determined by the cavitation resistance of its xylem tissue.
  
  
  METHODS
  Two species were selected with contrasting cavitation resistance (beech and poplar), and potted juvenile trees were exposed to a range of water stresses, causing up to 100 % plant death.
  
  
  RESULTS
  The lethal dose of water stress, defined as the xylem pressure inducing 50 % mortality, differed sharply across species (1·75 and 4·5 MPa in poplar and beech, respectively). However, the relationships between tree mortality and the degree of cavitation in the stems were similar, with mortality occurring suddenly when >90 % cavitation had occurred.
  
  
  CONCLUSIONS
  Overall, the results suggest that cavitation resistance is a causal factor of tree mortality under extreme drought conditions.
authors.affiliation: INRA, UMR547 PIAF, F-63100 Clermont-Ferrand, France.
authors.forename: Têtè Sévérien
authors.initials: TS
authors.lastname: Barigah
authors.forename: Olivia
authors.initials: O
authors.lastname: Charrier
authors.forename: Marie
authors.initials: M
authors.lastname: Douris
authors.forename: Marc
authors.initials: M
authors.lastname: Bonhomme
authors.forename: Stéphane
authors.initials: S
authors.lastname: Herbette
authors.forename: Thierry
authors.initials: T
authors.lastname: Améglio
authors.forename: Régis
authors.initials: R
authors.lastname: Fichot
authors.forename: Frank
authors.initials: F
authors.lastname: Brignolas
authors.forename: Hervé
authors.initials: H
authors.lastname: Cochard
mesh_terms: D003681:Dehydration; D029964:Fagus / Q000502:physiology*; D006813:Humidity; D032107:Populus / Q000502:physiology*; D012987:Soil; D013997:Time Factors; D014197:Trees / Q000502:physiology*; D014867:Water / Q000502:physiology*; D052584:Xylem / Q000502:physiology*
chemical_list: D012987:Soil; D014867:Water
keywords: Fagus sylvatica; Populus deltoides × P. nigra; Water stress; beech; embolism; hybrid poplar; hydraulic failure; mortality; resilience; vulnerability curves